1. Field of the Invention
The invention relates to a wind-powered device for producing electrical energy.
The constant increase in the costs of fossil sources of energy, allied with a depletion of the fossil-fuel reserves—oil, coal, natural gas—and with an awareness of the imbalance that they cause in the carbon cycle, has resulted in numerous investigations intended to develop devices for producing renewable and inexhaustible energy, in particular wind-powered devices for producing energy.
2. Description of Related Art
There exist a great number of wind-powered devices for producing electrical energy. The general principle of these devices, which derives from the principle of the windmills used formerly for pumping water or grinding grain, consists in utilising the force of the wind in order to drive a shaft in rotation and to place an electrical machine, such as a generator, at the end of this shaft, so that it is able to convert the mechanical energy of the shaft into electrical energy. In order to do this, a wind-powered device typically includes a blade wheel that is suitable to ensure the setting of a shaft in rotation by conversion of the energy of the wind into mechanical energy, a rotor including magnets and coils, which is arranged at the end of the shaft and the rotation of which enables the generation of an inductive field which is picked up across the stator of an alternator, ensuring the production of an electric current.
In particular, it is known to arrange a plurality of wind turbines in a given space, in order to set up a wind-powered power station. Each wind turbine of the wind-powered power station includes a shaft, at one end of which an electrical machine, such as a generator, is arranged. The currents generated by this plurality of generators are added up by the wind-powered power station for the purposes of being able to be conveyed by a network for transmitting electricity to users.
Since the amount of energy produced by a wind turbine is, in a first approximation, proportional to the speed of rotation of the rotor of the electrical machine, itself dependent on the speed of rotation of the wind turbine, the known devices have recourse to blades that are as large as possible, so as to enable high speeds to be attained, even in low wind.
Furthermore, large blades enable a torque to be attained at start-up that is sufficient to start the wind turbine.
The drawbacks of such a device relate to the complexity of the device, in particular as far as the design of the blades is concerned, the difficulties of installation and implementation, the manufacturing costs, the noise generated by the rotation of the blades, etc. Such devices are therefore reserved for large producers of energy, have to be installed far from dwellings, and for this reason are totally unsuitable for urban or periurban domestic use.
In order to facilitate the start-up of wind turbines without nevertheless resorting to oversize blades, it is known to attach a device, in particular an electric device, for assisting the start-up of the wind turbines.
This solution only reinforces the drawbacks linked to the complexity and cost of such a device.
In order to overcome these problems in part, other devices have been proposed in order to increase the speed of rotation of the rotor and the torque at start-up without nevertheless resorting to oversize blades. For example, JP 2004-162684 describes a wind-powered device for producing electrical energy including two wind turbines that are suitable to rotate in opposite directions, one including the rotor of the alternator, and the other including the stator of the alternator. Consequently the apparent speed of rotation of the rotor in relation to the stator is approximately doubled in comparison with a device with fixed stator.
The drawback of this device relates, in particular, to an output that is not highly optimised, because of the arrangement of the blade wheels opposite one another, the leeward wheel then necessarily catching the wind less that the windward wheel. Moreover, the windward wheel creates turbulences that are capable of impeding the good rotation of the leeward wheel.
JP 2004-340116 describes a wind-powered device including a shaft, around which a plurality of blade wheels are arranged and at the end of which a generator is arranged. Such a device therefore enables the generation of a substantial torque at start-up, enabling the driving of the rotor of the generator without any auxiliary device for assisting start-up.
On the other hand, the speed of rotation of the rotor is limited and remains dependent on the dimensions of the blade wheels arranged on the shaft of the device.
Furthermore, the problem linked to the arrangement of the windward and leeward wheels remains.